The present invention relates to a crutch for medical applications, and more particularly to a crutch comprised of contoured pipe elements which are adapted to withstand the working loads of the user and the formation pressures during its manufacturing process.
For the sake of assisting the walking activities of many disabled persons, crutches have been widely employed over the past years.
As shown in FIGS. 5 to 7 attached, the conventional structure of these crutches is a bottom leg 100 with a pair of parallel side rails 101 and 101' affixed thereto and extending upwards with a predetermined space therebetween to be connected with a cross member or armpit rest 102 at their top portions.
Between the side rails 101 and 101' an intermediate cross member or hand hold 103 is provided at an adjustable distance corresponding to the length of the arm of the user from the armpit rest 102. Hand hold 103 is adjustably attached to the side rails 101 and 101' by a bolt 104 extending through a selected pair of a plurality of equally spaced holes in the side rails 101 and 101' and the aligned hole in the hand hold 103. The bolt 104 is tightened by a nut 1065, such as a wing nut.
Each of the side rails 101 and 101' is bent at two locations between the upper and lower bolts 104 and 106 to give a converged shape at the corresponding locations of the crutch.
In the past, such crutches had been made of woods but the necessity to the protection of nature and the heavy weights of the wood constructions declined their popularity. As the substitute, aluminum pipes of a circular cross section are being employed to manufacture the crutches.
In order to secure these pipe members to each other, screw holes must be provided at the convex surfaces of the pipe materials which is not an easy task. Even if they are secured successfully, the round surfaces of the members allows line contacts only which cause an insufficient force of engagement between the members resulting in wearings and crackings at the screw bolts before long under the working loads of the crutch. It should be understood that such loosen crutch can no longer give its function.
In an effort to solve this problem, a separate reinforcement 108 was suggested to attach the lower portions of the member 100, 101 and 101' in engagement in order to prevent a loosening or play of the supports during use of the crutch. However, if this reinforcement is not precise and the crutch is used for certain period of time, the members become gradually disengaged causing a feeling of uneasiness of the user all the time.
U.S. Pat. No. 4,733,682 discloses a crutch having a pair of bow members (side rails) which is crushed at their lower ends to remove protruding corners from the bow members for the purpose of achieving a tapered, streamlined, safer configuration. A leg carrier tube (bottom leg) of constant circular cross section is fastened to the bow members at their uncrashed, round surfaces at the upper side and at their crushed flat surfaces at the lower side.
Also, the descriptions of the above patent draws an attention to the fact that the full flattening of the blow members to be in contact with the leg carrier tube had been caused weak points in the crushes.
Furthermore, when the tubular members are subjected to a bending process even under a roller, it is a must to insert a reinforcing core to the inner diameter of the member before the bending operation to prevent a crush or crack otherwise present at the bending point of the member. This is because the bending should be performed on the round surface of the tubular member which, in addition, is made of an aluminum of weak strength. At this instant, only one member at a time could be loaded on the bending machine which is adverse to the profitable productivity.
Another disadvantage resides in the cumbersome and time consuming punching operations wherein a clamping means for holding a pipe against the depressions and a reinforcement core in the tubular member are necessary everytime to secure a precise punching and to prevent a crush in the member. The alternative to this is to use a tubular member of thicker walls which is disadvantageous.
In practical use of the crutch, it is subjected to loads in certain directions, i.e. lateral only. Therefore, with round pipes, a means for reinforcing their engagement in the lateral direction is lacking.
It is an object of the present invention to enhance the engagement force between the tubular elements of the crutches to provide a continued integrity of the crutches without a deforming process for crushing the elements which essentially sacrifices the strength and/or the continued integrity of the crutches.
It is another object of the present invention to provide a means for increasing the resistance of the tubular members to the forming depressions in the bending and punching processes.